|  | 2.3 | Switching and VLANs
| 2.3.1 | Describe the two basic operations of a switch
Switching is a technology that decreases congestion in Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) LANs by reducing traffic and increasing bandwidth. LAN switches often replace shared hubs and are designed to work with existing cable infrastructures so that they can be installed without disrupting existing network traffic. Today in data communications, all switching equipment perform two basic operations: Switching data frames-This happens when a frame arrives on an input media and is transmitted to an output media. Maintaining switching operations-In this operation, switches build and maintain switching tables. The term bridging refers to a technology in which a device known as a bridge connects two or more LAN segments. A bridge transmits datagrams from one segment to their destinations on other segments. When a bridge is powered on and begins to operate, it examines the MAC address of the incoming datagrams and builds a table of known destinations. If the bridge knows that the destination of a datagram is on the same segment as the source of the datagram, it drops the datagram because there is no need to transmit it. If the bridge knows that the destination is on another segment, it transmits the datagram on that segment only. If the bridge does not know the destination segment, the bridge transmits the datagram on all segments except the source segment (a technique known as flooding). The primary benefit of bridging is that it limits traffic to certain network segments. Both bridges and switches connect LAN segments, use a table of MAC addresses to determine the segment on which a datagram needs to be transmitted, and reduce traffic. Switches are more functional in todays networks than bridges because they operate at much higher speeds than bridges and can support new functionality, such as virtual LANs (VLANs). Bridges typically switch using software; switches typically switch using hardware.